The present invention relates generally to a sole structure for a sports shoe, and more particularly, to an improvement in the sole structure for achieving a lightweight and securing stability and enhancing resilience at the time of heel strike onto the ground.
Japanese patent application laying-open publication No. 11-203 shows a sole structure for a sports shoe having an upper midsole and a lower midsole that are disposed at the heel portion of the shoe and that are formed of soft elastic materials, and having a wavy corrugated sheet that is disposed between the upper midsole and the lower midsole.
In this case, since a midsole heel portion has the wavy corrugated sheet interposed thereinto, the midsole heel portion generates a resistance force to restrain a lateral deformation of the midsole heel portion at the time of heel strike onto the ground. Thereby, a lateral swing or leaning sideways of the sole heel portion is prevented and stability on heel striking onto the ground is secured.
However, in this case, the upper and lower midsoles of soft elastic materials are provided on the upper and lower sides of the wavy corrugated sheet. As a result, it has a deficiency that the weight of the entire sole structure becomes heavy.
On the other hand, U.S. Pat. No. 6,487,796 discloses a sole structure having a plurality of resilient support elements at the sole heel region. The top surfaces of the resilient support elements are inclined downwardly toward the heel central portion. Each of the resilient support elements has an indentation formed around the outer circumferential surface of the elements. That is, in this case, the height of each of the resilient support members is highest at the sole outer circumferential edge portion and gradually lowered toward the sole central portion and lowest at the innermost position of the sole (see FIGS. 6 and 7). Also, the indentation is formed at a position that causes the resilient support element to deform to fall toward the heel central portion when the compressive load is applied.
In this case, the sole structure is constructed by sandwiching the resilient support elements between the heel plate and the base without utilizing a relatively heavy soft elastic material, which makes it possible to decrease the weight of the entire sole structure. Also, U.S. Pat. No. '796 describes that since the periphery of the calcaneus of the foot of a wearer is supported at the lower-side inclined surface on the top surfaces of the resilient support elements a compressive force applied from the calcaneus at the time of impacting the ground on the heel causes the resilient support elements to deform toward the heel central portion thus improving the stability of the shoe in the lateral direction.
However, in the structure shown in U.S. Pat. No. '796, it is directed to achieving a lateral stability at the time of heel strike onto the ground by causing the resilient support elements to deform and fall toward the heel central portion at the time of heel strike onto the ground in such a way that the heel portion of the foot moves downwardly toward the intermediate regions between the resilient support elements. Therefore, it does not have a sufficient resilience as a sole heel region which is required from heel-in to heel-off.
An object of the present invention is to provide a sole structure for a sports shoe that is lighter in weight and that can secure stability and improve resilience at the time of heel strike onto the ground.
Other objects and advantages of the present invention will be apparent from the following description.